PRIMARY LENS LUXATION IN RAT TERRIERS

Rat Terrier breeders and owners need to be aware of an eye issue that was recently discovered in the Rat Terrier breed. It is an issue that has lurked unknowingly in the breed for many years. The good news is, as of October 2009, an invaluable “test” became available to find the DNA marker for Primary Lens Luxation. When selecting a Rat Terrier, ask for PROOF of their testing results. If the dogs’ parents have not been tested or proof is withheld … RUN.

We need to quit whispering about defects, and gossiping about defects, and instead set up a sound program that allows the standard selection procedures to go on so that we breed good dogs and avoid major defects.

-- Dr. George A. Padgett, DVM


WHAT IS PLL? Primary Lens Luxation is the dislocation or displacement of the lens within the eye. The lens is the clear structure in the eye, consisting of two rounded or convex surfaces, that focuses light rays to form an image onto the retina. Normally the lens is suspended between the iris (the colored portion of the eye) and the vitreous (the clear gel in the back of the eye), and is held in place by small fibers called zonules or suspensory ligaments. Should the zonules break, the lens can either become partially dislocated (subluxated) from its normal position or completely dislocated (luxated). When the lens detaches and falls forward into the anterior chamber in front of the pupil, it is called an Anterior Luxation. When it falls back into the rear portion of the eye, it is called a Posterior Luxation.

HOW DOES A DOG GET IT? Primary Lens Luxation is an inherited disorder in which the zonules or suspensory fibers degenerate. The condition occurs mainly in the terrier breeds, namely the Parson Russell Terrier, Tibetan Terrier, Smooth Fox Terrier and Rat Terrier. Primary luxations are also seen in the Border Collie, the Australian Cattle dog (blue heeler), and sporadically in other breeds. Although the underlying reasons for the lens luxation are not well understood, inflammation or a defect in the zonules may play a role. With primary lens luxation, both eyes are prone to dislocation of the lens.

HOW CAN I TEST MY DOG? Before October 15, 2009 there was NO test for PLL. Through the partnership of the University of Missouri College of Veterinary Medicine and OFA (Orthopedic Foundation for Animals), there is NOW a DNA test for this mutation. The cost is $65.

HOW IS THE TEST PERFORMED? A Test Kit will include a cheek swab and DNA marker card with instructions how to perform this simple test. The inside of the dog’s mouth/cheek is swabbed to collect cells and saliva. Then the saliva is spread onto the card. The card is sent to OFA.

WHAT WILL THE TEST REVEAL? The DNA test results will categorize dogs as follows: Affected, Carrier, or Normal/Clear
AFFECTED: This finding indicates that TWO copies of the disease gene are present in the dog. Unfortunately, the dog will be medically Affected by the disease. Appropriate treatment should be pursued by consulting a veterinarian. An AFFECTED dog will have 2 mutated copies of the gene. The vast majority of these dogs will luxate at 4-8yrs of age, the typical age of onset for PLL. There were a few dogs in the study group that tested as AFFECTED but did not luxate until after 8 yrs of age, and some dogs testing AFFECTED have died from other causes without luxating. A search of published veterinary literature revealed that about 10% of the dogs reported to be clinically Affected with PLL had onset of symptoms after 8 yrs of age. Because of this, the test results will say “AFFECTED/HIGH RISK.
CARRIER: This finding indicates that ONE copy of the disease gene is present in your dog, but that it will not exhibit disease symptoms. Carriers will not have medical problems as a result. Dogs with Carrier status can be enjoyed without the fear of developing medical problems but will pass on the disease gene 50% of the time. Carriers have one normal and one mutated copy of the gene. They could pass either the normal copy or the mutated copy on to their offspring. Because there were very few cases of dogs in the research groups testing CARRIER who did appear to have PLL, the test results will say “CARRIER/LOW RISK.
NORMAL: This finding indicates that the GENE IS NOT PRESENT in your dog. Therefore, when used for breeding, a Clear dog will not pass on the disease gene. A dog testing NORMAL has 2 normal copies of the gene, is not at risk for developing PLL, and can only pass a normal copy of the gene to any offspring. Some sites use the word Normal or Clear. Both these words mean the same thing. It means that the dog in question is NOT a Carrier nor is it Affected.
CLEAR BY PARENTAGE (CBP): You may see health clearances with the wording "Cleared By Parentage" or "CBP" on breeder sites. This means both sire and dam are proven Normal/Clear and that pair bred together can never produce an Affected or a Carrier. Some sites use the word Normal or Clear. Both these words mean the same thing. It means that the dog in question is NOT a Carrier nor is it Affected.

RECOMMENDED READING  
Canine Lens Luxation Basics

About the PLL Test

Orthopedic Foundation for Animals (OFA)

American Rat Terrier Association

This album contains the OFA Primary Lens Luxation Results on our dogs.

Jeter - Normal/Clear

Dinger - Normal/Clear

Peyton - Clear By Parentage

Taz - Clear By Parentage

Stormy - Normal/Clear

Chatter - Carrier/Low Risk

Rumor - Carrier/Low Risk

Dazzle - Clear By Parentage

Peanut - Clear By Parentage

Java - Pending

These Puppies Have All Found Their Forever Homes

305-382-2581 or AWerner12@aol.com

Black & White Litter 

Dam: GRCH RaganRat Best Kept Secret CGC

Sire: GRCH 'PR' Ratitatt All ABuzz About Jeter BISS, BIMBS, RBIMBS, CGC

Looney Tunes Litter

Dam: GRCH Jackpot Hurricane Warning

Sire: GRCH 'PR' Ratitatt All ABuzz About Jeter BISS, BIMBS, RBIMBS, CGC

AKC BREED STANDARD THE RAT TERRIER BREED STANDARD (Official AKC) GENERAL APPEARANCE

The Rat Terrier was originally bred for ratting and farm work. A multipurpose companion dog that is capable of hunting rodents and vermin above and below ground, and to course small game. He is a sturdy, compact, small-to-medium sized particolored dog giving the appearance of elegance and fitness, denoting speed, power and balance. Honorable scars or a couple of broken or missing canines or incisors teeth are not to be faulted. The following is a description of the ideal Rat Terrier. Variations are penalized to the extent of the deviation.

SIZE, PROPORTION, SUBSTANCE –

SIZE – There are two separate size divisions. MINIATURE – At least 10 inches, not to exceed 13 inches.  

STANDARD – over 13 inches, and up to and including 18 inches in height measured at the withers. Any dog six months of age or older measuring less than 10 inches, or any dog over 18 inches are to be disqualified.  

PROPORTION - The Rat Terrier is just slightly longer than tall. The height, measured vertically from the ground to the highest point of the withers, is slightly less than the length, measured horizontally from the point of the shoulders to the point of the buttocks. Shortness in leg is a serious fault.

SUBSTANCE – Moderate bone in proportion to size. A well-balanced, hard-muscled dog with smooth lines under taut skin. This dog should not be rangy nor fine boned and toyish, and never bulky or coarse. They are shown in good, hard physical working condition.

HEAD – The HEAD resembles a smooth, blunt wedge from a front or profile view. When seen from the front, the head widens gradually towards the base of the ears in an unbroken line and is well filled up under the eyes. EXPRESSION is intelligent, alert and full of interest.

EYES - are not large. They are obliquely set wide apart and are oval in shape. Eye color varies with coat color from darkest brown to hazel. Eye rim pigmentation corresponds with nose color and facial markings. Gray eyes are acceptable in blue or blue-fawn dogs only, being a serious fault in other colorations. Any blue in the eye(s) is a disqualification.

EARS – Set on the top outer edge of the skull, V-shaped, with the length in proportion to the head moderately pointed at the tip. When viewed from the side, the base of the ear is on line with the outer corner of the eye. Ears should match in shape and carriage when alert, and can be carried erect, semi-erect and tipped, or button without preference. When alert, a rose ear is a fault. Cropped ears are a dis qualification.

SKULL –When viewed from the front the skull is moderate in width, relatively flat on top, and rounded at crown and the sides as it widens s moothly from the corner of the eyes to the base of the ears. The occiput is not prominent. The cheeks are flat and well-muscled, but never bulging. The STOP is moderate but distinct.

MUZZLE is strong, just slightly shorter in length than the skull and tapers smoothly along the sides to the nose.  

NOSE color corresponds with the body color and is entirely pigmented. Flesh-colored noses are considered a fault in lemon or light apricot colorations while being a serious fault in other colorations. Seasonal fading is permitted. LIPS are clean and tight, and correspond in color with the nose leather or may be pink; either solid or spotted is acceptable. The lower jaw and teeth are strong and well developed with no sign of being snipey or weak.

BITE- A scissor bite is preferred. A level bite is acceptable.

NECK TOPLINE, BODY –

NECK – Length of neck is in proportion to the head. Strong, arched along the crest and dry, the neck blends smoothly into the flat shoulder blades.

TOPLINE – Smooth and blending from the back through the loin and set of the tail.

BODY – The body is compact, strong and flexible with well sprung ribs. The brisket extends to the elbow. When viewed from the front, the ribs appear to be oval. The Rat Terrier, while muscled and fit, has flat muscles that blend into the body. The chest is moderately wide and well filled with a discernible forechest. The underline ascends gradually with the ribs extending well back to a moderate tuck-up.

BACK - The back is level and firm from the withers to the loin. The short loin has a slight muscular arch blending into the gently rounded croup.

TAIL – The tail set is a continuation of the spine. Tails are customarily docked between the second and third joint, or can be a natural bobtail or left naturally long and tapering to the hock joint. Length is unimportant. The carriage is variable depending on attitude, carried from slightly below horizontal to almost erect, but not over the back or a ring tail.

FOREQUARTERS – The shoulder blades are well laid back with flat muscles providing enough space between the shoulder blades to allow for free movement. The shoulder blades and the upper arms are nearly equal in length and well set back so that the elbows fall directly under the highest point of the shoulder blade. The depth of the body at the elbow is the same distance as from the elbow to the ground. The forelegs stand straight and parallel with elbows turning neither in nor out. The pasterns are slightly sloping when viewed from the side.

FEET are oval in shape. The toes turn neither in nor out, are compact, moderately arched, with thick pads and strong nails. The front dewclaws may be removed.

HINDQUARTERS – The hindquarters are muscular but smooth and in balance with the forequarters. They should not be bulging or coarse. Stifles are well-bent with short hocks that are parallel and perpendicular to the ground. The hind feet although slightly smaller are similar to the front feet. Rear dewclaws are removed.

COAT – Short, close lying, smooth and shiny coat. Texture varies; a very slight ruff or wave along the back is allowed, but undesirable. Any suggestion of kink or curl is cause for disqualification. Whiskers must not be removed. Absence of coat (total genetic hairlessness) is a disqualification.

COLOR - Any variation of Pied patterning is acceptable. Pied is described as comparatively large patches of one or more colors in combination with white. Except for the "solid white" extreme piebald dog with only mottled/spotted skin; Rat Terriers are never a solid ground color without white markings, or bi-colored without one color being white. Acceptable colors with or without "tan points", include the predominate Black; or Chocolate, Red, Apricot, Blue, Fawn, Tan, Lemon, or White. Intense, dark shades of color with clearly defined and delineated coloration is preferred. White on the body is preferred to be between 10% and 90%, but all Patterns; spotted, patched or splashed with white in conjunction with (or without) any combination of white on the face, head or ears are equally acceptable without prejudice. "Tan Points" are common and vary in shades of cream to rust. Badger markings are acceptable. Speckling, ticking and ...